1. Field of the Invention
The present invention relates to a digital TV, and more particularly, to a digital TV receiver compensating a symbol synchronization signal and a carrier signal by detecting multipath channel information.
2. Discussion of the Related Art
VSB (vestigial sideband) systems have been adopted as the standard of a terrestrial channel transmission method for digital television (DTV). Less efforts were made to research and develop antennas for a digital TV receiver. Recently, new concepts and ideas for the antennas are actively proposed.
It has been known that standardization (CEA/EIA909) of the digital TV receiver antenna was completed by ATSC (advanced television system committee). Besides, it has been verified that ATI (Next Wave) corporation has experimentally applied the antenna to digital TV, and its field test is still in progress.
Meanwhile, since the digital TV market itself is still at the early stage of development, many efforts were made to the development of digital TV receiver antenna technologies for the applications to radio communication systems such as mobile terminal, military radio communication, etc. Such antenna technologies are very complicated and highly expensive, whereby many technological efforts are needed.
A smart antenna applied to digital TV removes multipath for indoor reception and improves quality of signal, thereby enabling to enhance reception performance. Especially, such a smart antenna brings a remarkable effect under the environment that a separately-located transmitting tower exists according to broadcast channel. In this case, the conventional method of detecting multipath information observes spectrum flatness of a reception signal or uses a tap coefficient or tip energy of a channel equalizer.
However, such methods mostly detect information from the channel equalizer, in which precise convergence of the channel equalizer should be presumed to detect the correct information. Hence, information detecting time is elongated. Moreover, in case that the channel equalizer is unstable, incorrect information or non-information is detected.
FIG. 1 is a graph of frequency spectrum of a general VSB signal, in which carrier information (pilot) and symbol timing information are located at a DC position and a symbol frequency, respectively. Hence, the channel equalizer compensates such distortions to improve reception performance. Yet, if a specific multipath signal is generated to attenuate carrier information and symbol synchronization information, the carrier and symbol synchronization recovery units at a front side of the channel equalizer are degraded in performance or fail to operate so that channel equalization cannot be performed. This is fatal to the receiving performance of the VSB systems.